A rather intense February for all – don’t you think? Surviving a Maine winter is routine for Peaks Islanders, and for the birds, even the demure Black Guillemot. But, this year was a little tough. As we crawl into warm beds at night, where do the birds go? Marty pondered this question one day while watching the birds at his feeder: “How does something like a blizzard affect our feathered friends? Do they just stay in? Does it bother them?” While watching birds at Wharf Cove I was similarly challenged with questions from Peggy, Carol, and Jamie, all clothed in heavy parkas, hats, gloves, and boots: “How do our birds stay warm?”
Good questions and good timing, as I am deep into reading a book about feathers. In it are discussions about the insulation properties of feathers. This highly acclaimed book is simply called “Feathers” – (‘The Evolution of a Natural Miracle’). Author Thor Hanson clearly and with a great writing style describes what all the fluff in feathers is about and how they keep birds warm in blizzards, and cool when it is hot. As a graduate student working with the well-known author, Professor Bernd Heinrich (U. Vermont), Thor describes stalking small birds in the Maine woods. He wanted to learn how they survive the frigid nights such as the one that he, himself survived - at minus 27 degrees F - sleeping in his “plush goose down sleeping bag”. Thor wondered that night, how a Golden-crowned Kinglet, with the smallest body weight of any bird in those woods, stays cozy in its feather coat? The paragraphs below highlight key points on the properties of feather insulation, as he describes in ‘Feathers’.(1)
Each bird species must find shelter somewhere, perhaps finding favorite hideouts, or protected haunts at sea. But, their feathers are the key to their survival. Plumages are complicated. Take for example how visually different each feather is on a single bird, and then compare those findings to a vastly different species, say – a kinglet and a loon. But basic feather structures remain the same. Each plumage configuration serves birds for all of their activities, and especially for their insulative power. The fluffy whitish-grey down feathers, found beneath their outside (contour) feathers, arrange themselves nicely using little muscles at the base of each feather quill. The down feathers interlock in such a way that a warm air barrier is formed next to the bird’s warm skin. Birds look more fluffy or puffy when cold, appearing bigger in size, as their feathers adjust. Sea ducks’ down feathers can be as thick as 1/3 to 2/3 inch. We wear thick down coats (historically - eider down) for the same reason – insulation against the cold.(1) A thick layer of fat below the skin of sea ducks acts as another level of defense against the cold (2).
If these down feathers get wet, all bets are off. So what protects these down feathers? How does a bird living on the sea stay watertight? How do ducklings with only down feathers stay dry as they try out their first paddling skills? Even though down feathers are soakable; they apparently have some degree of water resistance in ducklings.(1)
A gland at the base of most birds’ rumps provides a lipid rich secretion. Have you noticed that watching a bird while it preens, how it continually reaches to its rump? With its beak, the bird takes this oil and evenly distributes it. This oil acts as a water-repellent. It makes sense since oil and water do not mix. And, sea ducks have a large oil gland as compared to most birds. But that is not all of it. Recent studies using electron microscopes show that the microstructure of contour feathers also aids in repelling water. The barbs and barbules of feathers form an interlocking matrix that prevents water droplets from penetrating past the contour feathers – thereby protecting the underlying down feathers. These microstructure properties of feathers are attracting a lot of interest from not only ornithologists but from folks interested in environmentally friendly waterproof materials.(1)
(Cormorant feathers differ from other birds in their insulative properties, but let’s save that discussion for later when these birds return to PI.)
Birds also shiver, requiring more calories, so an adequate food supply is important. If a storm lasts too long, birds are at risk. Snow Buntings have adapted another strategy for living in northern climates: they conserve their energy levels by withholding shivering until the temperature drops below 10 degrees. How do they do it? An anonymous observer saw these small buntings (winter plumage - white bellies with dashes of a ginger brown and grey on their backs) this winter on the Backshore.
There is more. Most birds, especially large footed ones such as gulls, sea ducks, and loons conserve heat in their feet by controlling blood flow there – a unique countercurrent heat exchange. These larger birds also have a shunt system that allows more direct heat exchange between these leg and foot arteries and veins.(3)
A countercurrent heat exchange exists in the head as well (3). Still some birds attempt to reduce heat loss to the head by using the ‘tuck technique’. This winter the Red-breasted Mergansers are frequently seen with their heads tucked under their back feathers. Watch them closely, they are not sleeping, they are paddling about – especially as a pair. One eye must be used for navigation, and keeping an eye on its mate, as the bare skin and beak are protected.
Back to the Backshore Birds: Late February bird sightings included most ones that were seen in January, however, the absence of cormorants or grebes was duly noted. Perhaps I missed them. Yet, sighting four Canada Geese at Woodcutter’s Beach, feeding along the ice margins was unusual. Michelle also observed these geese here and at Centennial Beach.
Canada Geese at ice margins - Woodcutter's Beach
A number of Common Loons were scattered offshore, some of which appeared closer to shore than seen previously. Kathy concurred.
A large flotilla of birds was seen far offshore in the shipping channel between Peaks and Long Islands. Even though a spotting scope would have been handy, binoculars were sufficient to identify some birds as loons (> 10 on one day) and some as gulls, probably Herring Gulls. Were the grebes out there? On this very cold day the fishing vessel ‘Jacob and Joshua’ shared the space and resources with these birds.
Several large groups of Common Eiders (The total number ranged from ~500-700 - similar to January counts.) along the shore shared their favorite hunting grounds (South Shore/Whitehead Passage, Alder Brook Road, and the Bicycle House #500) with a much smaller number of scoters.
Last February 2014 large flocks of scoters were observed off the Backshore, as compared to a scattering of them this year. Nor, have I seen scoter flocks leaving Casco Bay at night and returning to it through Whitehead Passage - as seen in the past three years. On February 25, a large flock of dark birds was seen off Whitehead, Cushing Island. Were they scoters? Has anyone seen large flocks of scoters this year?
Large Scoter Flock
There is nothing like the sights of a Bald Eagle to stir up a scoter flock of ~500. Last February 2014 close to shore at the Heart House (Onway and Seashore Aves) Sam, my husband, and I watched a large flock of scoters foraging – scoter-style. Scoters (mostly Black Scoters) differ from the eiders in their foraging style: The eiders dive independently of each other while the scoters dive nearly simultaneously. In a very large flock such as this one, the birds appear to peel-off and dive in a flowing fashion – remember synchronous swimming shows? This latter strategy served the scoters well in discouraging the eagle from obtaining its next meal. Each time this large bird fell from the sky for a closer look at the little black birds, the scoters disappeared – almost all at once. Confusing to the eagle? Perhaps so, the eagle lost interest after several passes. But, what are the scoters doing underwater? Wouldn’t ~ 500 scoters make for a crowded place down there? Are there any collisions?
Peggy asked, “Why do the eiders stay in large rafts?” Carol noted that the Emperor Penguins (‘March of the Penguins’) in the Antarctic winters huddle in groups, each individual taking a turn on the periphery where it is most exposed to the cold. Do the eiders and scoters, especially at night when they travel out to sea together, huddle close enough to gain some warmth from each other? An individual in a crowd (think fish schools) is less likely to become a predator’s meal. I have observed the eider flocks get agitated to the point of panic when a loon is prowling about (Subsurface loons have been known to come from beneath, and then ‘spear’ another loon - territoriality issues? ). A Harbor Seal will send the eiders into an absolute frenzied panic – propelling themselves over the water, 'bellying-up'* to the rocks, and scrambling to safety. Or is ‘rafting’ part of their social structure? Rafts provide more eyes to find the best feeding spots, or better opportunities for finding a partner? Perhaps rafting serves all of above, and more?
Several Common Goldeneyes, a pair of Barrow’s Goldeneyes, a couple of Long-tailed Ducks, Buffleheads, and one Black Guillemot were seen scattered along the South and Backshore. Several Long-tailed Ducks were seen in Casco Bay between Peaks Island and Portland. I was confused about the identification of two sea ducks on the South Shore, so I brought along Kathy to aid in identification. We both agreed, based on the white crescent behind the beak, that they were two female scaups. The two species of female scaups (Greater and Lesser) look very similar and they are hard to differentiate, however, the former is more likely to be here. We also noticed that they stuck together, again similar to synchronous swimmers – or just a tight friendship.
The importance of feathers’ protective power was brought to our attention again, as Jamie, Peggy, Carol and I observed a female Common Goldeneye perched on an isolated rock in Wharf Cove. Goldeneyes do not come ashore in the winter months. She was preening – anxiously preening her breast feathers. A dark smudge (oil sludge?) was seen and that spot was the focus of her concern. We discussed why the cleanliness of her contour feathers was important to her. The precise interlocking of the barbs and barbules that keep water droplets out, could be compromised. A water leak could occur through this normally impervious barrier allowing the down feathers to be wetted, with a loss of warm air over her skin. She continued her preening, to ‘fix’ her feathers, as we left at dusk, and as she faced a frigid night at sea. Peggy wanted to know if the goldeneyes stay alone at night and where do they sleep? Where did she go?